This invention relates to a disc reproducing apparatus for reproducing recorded data recorded on an optical disc, and to a disc recording apparatus. Such recorded data may be, for example, voice data, music data or even video data. For simplicity of explanation only, the recorded data is referred to as voice data throughout the specification, including in the claims. More particularly, it relates to a disc reproducing apparatus comprising a reproducing section for reproducing recording data recorded on an optical disc and a memory for transiently storing playback data produced by the reproducing means, in which data stored in the memory is read out at a constant rate and supplied to an output. The invention further relates to a disc recording apparatus for recording data onto a disc, in which input data transiently stored in a memory is read out of the memory for recording onto the disc.
Optical discs are used extensively as a recording medium, and they are capable of high speed accesses and semi-permanent data storage. Disc reproducing apparatuses for reproducing data recorded on optical discs are known as CD players and have been introduced commercially.
An optical disc has its entire recording region divided into a data recording area, for recording voice data to be reproduced and a lead-in area for recording, which is not to be reproduced per se, so-called table-of-contents (TOC) data, such as recording start addresses, recording end addresses or absolute time data.
Before reproducing the voice data recorded in the data recording area, the disc reproducing apparatus first reproduces the TOC data, representing the recorded contents of the voice data, from the lead-in area, for storage in a TOC memory. When a command is made to reproduce the voice data, the TOC data for the voice data designated for reproduction is read out from the TOC memory and the disc is accessed based on the readout TOC data, to reproduce the designated voice data.
The voice data recorded in the data recording area is recorded with encoding information for error correction, and an error detection operation is performed at the time of reproduction. If an error is found in the reproduced voice data, an error flag is set. This error flag is stored in an error flag memory, distinct from the voice data memory and the TOC memory. The reproduced voice data in error is processed, by a method such as by interpolation, corresponding to the error flag stored in the error flag memory.
Disturbances, such as vibrations, during reproduction of the voice data may cause reproduce skip due to abrupt track jumps. Although such reproduce skip may be prevented by providing a shock absorber mechanism to prevent the vibrations from being transmitted to the reproducing system, it is not desirable to provide such a shock absorber mechanism because the disc reproducing apparatus itself would be increased in size.
If a large capacity RAM is provided for storing the voice data reproduced from the optical disc (i.e., playback data), such that the playback data is temporarily stored in the RAM for subsequent reproduction, the playback data stored in the RAN may be again reproduced and outputted during a restoration operation for repairing the inadvertent track jump caused by such vibrations, so that voice data may be outputted continuously, despite track jumps.
However, it is necessary in this case to provide a separate TOC memory for storing the TOC data and a separate error flag memory for storing the error flags, which increases the size of the apparatus and increase production costs.
On the other hand, if the large capacity RAM is provided for storing the playback data for preventing the voice skip, a larger space needs to be provided for the RAN which also renders it difficult to meet the demand for size reduction.